Organic light emitting device and manufacturing method thereof

ABSTRACT

An organic light emitting device having a photonic crystal structure and a manufacturing method thereof are provided. The organic light emitting device comprises: a substrate through which light passes; a photonic crystal layer formed on the substrate and having a photonic crystal structure; an intermediate layer formed on the photonic crystal layer and having a large refractive index compared with the photonic crystal layer; a first electrode layer formed on the intermediate layer; a light emitting layer formed on the first electrode layer and emitting light according to current flow; and a second electrode layer formed on the light emitting layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2007-0119089 filed in the Korean IntellectualProperty Office on Nov. 21, 2007, the entire content of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an organic light emitting device whichcan improve optical efficiency by having a photonic crystal structure,and a manufacturing method thereof.

(b) Description of the Related Art

Organic light emitting devices (OLEDs) are self-luminescent devices thatemit light when electrons and holes are combined in a fluorescent orphosphor organic layer when current flows to the fluorescent or phosphororganic layer. OLEDs can be manufactured to be lightweight using lessnumber of components through a simple manufacturing process, and canprovide high-quality images and wide-view angles.

In an OLED, the external light emission efficiency becomes a standardfor deciding the light emission efficiency of a product. The externallight emission efficiency of the OLED is determined by the internalquantum efficiency and the optical coupling efficiency. The internalquantum efficiency is determined by the nonradiative recombination lossand the singlet-triplet branching ratio. The internal quantum efficiencycan be improved to 80% experimentally. On the contrary, it is recognizedthat the optical coupling efficiency is improved to 20% because it isrelatively quite low compared with the internal quantum efficiency.Accordingly, the research to improve optical coupling efficiency isunder way, and the development of related technologies is steadilyprogressing.

A total reflection occurring at an interface of each layer of theorganic light emitting device is a major factor lowering the opticalcoupling efficiency. The organic light emitting device is formed of aplurality of air layers. The total reflection occurs mostly atinterfaces of the air layers. Conventionally, there are various knowntechniques for preventing total reflection and improving opticalcoupling efficiency.

Conventionally, there are known a method for patterning a silicamicrosphere on a substrate, a method for patterning a microlens on theback surface of a substrate, and a method for patterning a photoniccrystal structure on a substrate by an etching process. Such techniquesimprove optical coupling efficiency by scattering light at a substrateor at an interface of each air layer. In the techniques that have beenthusly studied and reported or known, light emission efficiency isimproved by forming a pattern of nanometer size. However, these knowntechniques are the result of the experiment carried out on samples ofareas of several mm size in order to form a nanometer size pattern.Therefore, in the case of actually manufacturing an organic lightemitting device product, it is difficult to form a nanometer levelpattern, and its manufacturing cost is high.

In addition, conventionally, there is known a result of improving lightemission efficiency by using an AAO (Anodic Aluminum Oxide) film havingholes of 400-450 nm. However, the method using an AAO film has a numberof problems including difficulty of manufacturing a large-area thin filmand low productivity. Moreover, the process using an AAO film isproblematic in that it is difficult to apply the process to a plasticsubstrate.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE INVENTION

The present invention has been proposed to solve the foregoing problemsof the prior art, and to provide an organic light emitting device whichis improved in optical efficiency compared with the conventional one.

Additionally, the present invention provides a manufacturing method ofan organic light emitting device which enables mass production andmanufactures a large-area organic light emitting device compared withthe conventional art.

An organic light emitting device according to an exemplary embodiment ofthe present invention comprises: a substrate through which light passes;a photonic crystal layer formed on the substrate and having a photoniccrystal structure; an intermediate layer formed on the photonic crystallayer and having a large refractive index compared with the photoniccrystal layer; a first electrode layer formed on the intermediate layer;a light emitting layer formed on the first electrode layer and emittinglight according to current flow; and a second electrode layer formed onthe light emitting layer.

The refractive index of the photonic crystal layer may be smaller thanor equal to that of the substrate. The photonic crystal layer may bemade of a polymer, and the substrate may be flexible.

The refractive index of the intermediate layer may be larger than orequal to that of the first electrode. The intermediate layer may be madeof one material selected from the group of oxides and nitrides. That isto say, the intermediate layer may be made of one or more materialsselected from the group consisting of SiNx, Si₃N₄, TiO₂, MgO, ZnO,Al₂O₃, SnO₂ and In₂O₃.

The organic light emitting device may further include an even portioncoated with a sol-gel solution on the intermediate layer, and the firstelectrode layer may be stacked on the even portion.

The photonic crystal structure may form a square lattice structure ortriangular lattice structure by having a plurality of photonic crystalunit patterns regularly arranged thereon. The shape of the photoniccrystal unit patterns may be one of a cylinder, a trigonal pyramid, anda square pyramid.

The first electrode layer may be made of a transparent conducting oxide(TCO) material.

A manufacturing method of an organic light emitting device according toan exemplary embodiment of the present invention comprises: forming aphotonic crystal layer on a substrate; forming an intermediate layer onthe photonic crystal layer; and sequentially forming a first electrodelayer, a light emitting layer, and a second electrode layer on theintermediate layer. The forming of a photonic crystal layer comprises:applying the material of the photonic crystal layer on the substrate;and forming a photonic crystal by imprinting the material of thephotonic crystal layer by using a mask having an inverted surface shapeof the photonic crystal structure.

In the forming of a photonic crystal layer, the mask may be pressed andheated after applying a polymer resin to the surface of the substrateand hardening the same in the imprinting, thereby forming a photoniccrystal layer. Alternatively, in the forming of a photonic crystallayer, in a state that the polymer resin in liquid form is applied tothe surface of the substrate and pressed by the mask in the imprinting,the polymer resin may be hardened by irradiating ultraviolet rays,thereby manufacturing a photonic crystal structure.

The forming of an intermediate layer comprises: dropping a sol-gelsolution onto the photonic crystal layer; and spin-coating the sol-gelsolution by spinning the substrate. At this moment, in the forming of anintermediate layer, crystallization may be induced by heating thesol-gel solution after spinning the substrate at 1,000-4,000 rpm in thespin-coating.

The forming of an intermediate layer may use any of chemical vapordeposition (CVD), plasma enhanced chemical vapor deposition, evaporatingdeposition, and sputtering.

The organic light emitting device according to the exemplary embodimentof the present invention has a merit that the light emission efficiencyis relatively high compared with the conventional one by having aphotonic crystal structure and reducing total reflection due todifference in refractive index.

Additionally, the manufacturing method of an organic light emittingdevice according to the exemplary embodiment of the present inventioncan mass-produce a large-area organic light emitting device at arelatively low cost compared with the conventional art by using ananoimprint process and a sol-gel method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of an organic light emitting deviceaccording to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a photonic crystal layer shownin FIG. 1.

FIGS. 3A to 3D are plan views respectively showing the arrangementstructures and unit patterns of photonic crystals which may be formed onthe photonic crystal layer shown in FIG. 1.

FIGS. 4A to 4C are cross sectional views showing the respective stepsaccording to a first exemplary embodiment for forming a photonic crystalof the photonic crystal layer shown in FIG. 1 by a nanoimprint process.

FIGS. 5A to 5C are cross sectional views showing the respective stepsaccording to a second exemplary embodiment for forming a photoniccrystal of the photonic crystal layer shown in FIG. 1 by a nanoimprintprocess.

FIGS. 6A to 6B are cross sectional views showing the step of forming anintermediate layer on the photonic crystal layer shown in FIG. 4C byusing a sol-gel method.

FIGS. 7A to 7C are cross sectional views showing the respective steps offorming an intermediate layer on the photonic crystal layer shown inFIG. 4C and then flattening the surface of the intermediate layer.

FIGS. 8A to 8C are cross sectional views showing the step of forming anintermediate layer after flattening the surface of the photonic crystallayer shown in FIG. 4C.

FIG. 9 and FIG. 10 are graphs comparatively illustrating the lightemission amount of the organic light emitting device having a photoniccrystal structure shown in FIG. 1 and the light emission amount of anorganic light emitting device having no photonic crystal structure inthe prior art, respectively, by simulation.

FIG. 11 is a graph showing light emission amounts according towavelength using the organic light emitting device having a photoniccrystal structure shown in FIG. 1 and the organic light emitting devicehaving no photonic crystal structure.

FIGS. 12 and 13 are views showing a character represented by using theorganic light emitting device having a photonic crystal structure shownin FIG. 1.

DESCRIPTION OF REFERENCE NUMERALS INDICATING PRIMARY ELEMENTS IN THEDRAWINGS

-   -   10: substrate    -   20: first electrode layer    -   30: light emitting layer    -   40: second electrode layer    -   50: photonic crystal layer    -   51: photonic crystal    -   60: intermediate layer    -   100: mask    -   200: sol-gel injector

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings so thatthose skilled in the art can readily carry out the invention. As thoseskilled in the art would realize, the described embodiments may bemodified in various different ways, all without departing from thespirit or scope of the present invention.

FIG. 1 is a cross sectional view of an organic light emitting deviceaccording to an exemplary embodiment of the present invention.

As shown in FIG. 1, the organic light emitting device OLED according tothis exemplary embodiment comprises, as basic components, a substrate10, a first electrode 20, a light emitting layer 30, and a secondelectrode layer 40. Particularly, the organic light emitting deviceaccording to this exemplary embodiment comprises a photonic crystallayer 50 having a photonic crystal layer for preventing internalreflection of light due to difference in refractive index between thesubstrate 10 and the first electrode 20 and an intermediate layer forsupplementing the electrical characteristic of the first electrodelayer.

The substrate 10 is a transparent substrate which externally diffuseslight generated in the organic light emitting device. A glass substrateis generally used as the substrate 10, and its refractive index is about1.5. The transparent substrate may be a crystalline quartz substrate oran amorphous glass substrate. In addition, the transparent substrate maybe a sapphire (Al₂O₃) substrate or a plastic substrate.

The first electrode layer 20 is laminated on one surface of theintermediate layer 60 after the photonic crystal layer 50 and theintermediate layer 60 are formed on the substrate 10. The firstelectrode layer 20 is a transparent conducting oxide (TCO) material, isgenerally made of an ITO (Indium Tin Oxide) material, and its refractiveindex is about 1.9. The first electrode layer 20 is referred to as apositive (+) electrode.

The light emitting layer 30 is an organic emission layer (EML), and islaminated on one surface of the first electrode layer 20. When currentflows from the first electrode layer 20 serving as a positive electrodeto the second electrode layer 40 serving as a negative electrode,electrons and holes are coupled at the light emitting layer 30. Due tothis, the light emitting layer 30 causes self light emission by whichlight is generated.

The second electrode layer 40 is laminated on one surface of the lightemitting layer 30. The second electrode layer 40 is made of a metalmaterial, serves as a negative (−) electrode, and is also referred to asa cathode layer.

The photonic crystal layer 50 is laminated on one surface of thesubstrate 10, and, as shown in FIG. 2, has a photonic crystal 51structure. The photonic crystal 51 is a structure for forming a photonicband gap (wavelength band of light that cannot pass through the photoniccrystal structure, and is arranged in a regular structure. The photoniccrystal 51 includes a region which light of a specific wavelength rangecannot permeate or which is lost upon reflection. For similar reason,reflection of light inside the organic light emitting device is reduced,thereby improving light emission efficiency. The photonic crystal 51structure will be explained in more detail below.

The photonic crystal layer 50 is made of a polymer. Therefore, thephotonic crystal layer 50 can be applied to a flexible substrate as wellas a glass substrate. The lower the refractive index of the photoniccrystal layer 50 is than the refractive index of the intermediate layer60, the higher the light emission efficiency is due to the photoniccrystal 51 layer. However, the lower the refractive index of thephotonic crystal layer 50, the greater the diffraction of light. Inorder to prevent additional total reflection, the refractive index ofthe photonic crystal layer 50 is preferably equal to or lower than therefractive index of the substrate 10. The photonic crystal layer 50 hasa permeation rate conforming to that of the substrate 10.

As the intermediate layer 60 is laminated on one surface of the photoniccrystal layer 50, it has a higher refractive index than that of thephotonic crystal layer 50. The conductivity and electricalcharacteristics of the first electrode layer 20 is affected much by itssurface shape. By the way, as explained above, the surface shape of thephotonic crystal layer 50 is not even due to the photonic crystal 51.Due to this, when the photonic crystal layer 50 and the first electrodelayer 20 come into direct contact with each other, this may cause a lotof leakage current. The intermediate layer 60 is formed between thephotonic crystal layer 50 and the first electrode layer 20, and playsthe role of suppressing current generation.

The intermediate layer 60 is made of one or more materials selected fromthe group of oxides and nitrides. That is to say, the intermediate layer60 is made of a material belonging to the group of oxides and nitrides,such as SiNx, Si₃N₄, TiO₂, MgO, ZnO, Al₂O₃, SnO₂, and In₂O₃.Particularly, ZnO used as the material of the intermediate layer 60 isin contact with the first electrode layer 20 made of an ITO material tocause the electrical characteristics to be properly exhibited.

The higher the refractive index of the intermediate layer 60 becomes,the higher the light emission efficiency becomes by means of thephotonic crystal structure. However, the lower the refractive index ofthe intermediate layer 60, the greater the diffraction of light. Inorder to prevent additional total reflection, the refractive index ofthe intermediate layer 60 is preferably equal to or lower than therefractive index of the first electrode layer 20.

In this way, in the organic light emitting device, diffraction orscattering of light is caused due to difference in refractive indexbetween the photonic crystal layer 51 and the photonic crystal layer 50.Due to this, in the organic light emitting device, total reflection oflight is reduced, and the efficiency of external light emission towardthe substrate is further improved. In addition, optimum light emissionefficiency, light intensity distribution in a far field, or lightintensity distribution according to observation angle determines thethickness of each air layer and the parameters of the photonic crystallayer by applying a simulation technique. The parameters of the photoniccrystal 51 structure are explained below with reference to FIGS. 3A to3D.

FIGS. 3A to 3D are plan views respectively showing the arrangementstructures and unit patters of photonic crystals which may be formed onthe photonic crystal layer shown in FIG. 1.

As shown in FIGS. 3A to 3D, structures of photonic crystals 51, 52, and53 are representative examples, and the following various structures canbe employed.

A plurality of unit patterns of the photonic crystal 51 as shown in FIG.3A are regularly arranged to form a square lattice structure, and has acylindrical shape. The unit patterns of the photonic crystal 51 shown inFIG. 3B also have a cylindrical shape, and are regularly arranged.However, the plurality of unit patterns of the photonic crystal 51 shownin FIG. 3B have a lattice structure in which they are arranged in atriangular shape. The unit patterns of the photonic crystal 52 shown inFIG. 3C form a square lattice structure as they have a trigonal pyramidshape and are regularly arranged. The unit patterns of the photoniccrystal 53 shown in FIG. 3D form a square lattice structure as they havea square pyramid shape and are regularly arranged. Besides, the unitpatterns of the photonic crystals may have a triangular latticestructure while having a trigonal pyramid or square pyramid shape.

In FIGS. 3A to 3D, reference numeral A is a distance between the unitpatterns of the photonic crystals 51, 52, and 53, and reference numeralD is a representative length of the unit patterns of the photoniccrystals 51, 52, and 53. If the unit patterns of the photonic crystal 51have a cylindrical shape, the representative length D of the unitpatterns of the photonic crystals 51, 52, and 53 means the diameterthereof. If the unit patterns of the photonic crystal 51 have a trigonalpyramid shape or square pyramid shape, the representative length D ofthe unit patterns of the photonic crystals 51, 52, and 53 means thelength of one side. In addition, reference numeral T of FIG. 2 means theheight of the unit patterns of the photonic crystal 51. Moreover, lightemission efficiency, light intensity distribution in a far field, orlight intensity distribution according to observation angle aredetermined in accordance with the parameters A, D, and T and shapes ofthe structures of the photonic crystals 51, 52, and 53. That is to say,when the distance A, height T, or representative length D between thephotonic crystals is changed, the degree of diffraction and scatteringof light is changed. In this manner, from the viewpoint of diffractionoptics, the more the diffraction and scattering of light occurs, thehigher the optical efficiency of the organic light emitting devicebecomes.

However, as a result of an experiment carried out by applying aplurality of simulation techniques, the distance A between the unitpatterns of the photonic crystals 51, 52, and 53 is most preferable whenit is ¼ to 2 times the wavelength of light. That is to say, if thedistance A between the unit patterns of the photonic crystals 51, 52,and 53 is less than ¼ times the wavelength of light, this isinappropriate because light can be permeated or totally reflected. Ifthe distance A between the unit patterns of the photonic crystals 51,52, and 53 is over 2 times the wavelength of light, this is notpreferable because the diffraction and scattering of light does notoccur.

The representative length D of the unit patterns of the photoniccrystals 51, 52, and 53 is most preferable when it is 0.1˜0.5 times thedistance A between the unit patterns of the photonic crystals 51, 52,and 53. That is to say, if the representative length D of the unitpatterns of the photonic crystals 51, 52, and 53 is less than 0.1 timesthe distance A between the unit patterns of the photonic crystals 51,52, and 53, this is inappropriate because the photonic crystal patternsare too small and thus light can be permeated and totally reflectedwithout diffraction or scattering. If the representative length D of theunit patterns of the photonic crystals 51, 52, and 53 is over 0.5 timesthe distance A between the unit patterns of the photonic crystals 51,52, and 53, this is not preferable because total reflection occurs.

A manufacturing method of a photonic crystal layer using a nanoimprintprocess according to a first exemplary embodiment of the presentinvention will be described below with reference to FIGS. 4A to 4C.

First, a material of the photonic crystal layer 50 is coated on onesurface of a substrate 10 by using a spin-coating and hardening process.As the material of the photonic crystal layer 50, a polymer is used.Then, a polymer resin is imprinted by heating and pressurizing by usinga mask 100 having an inverted shape of a photonic crystal structure.Then, the photonic crystal structure of a nanometer size formed on themask 100 can be easily transferred on the polymer resin, thereby forminga photonic crystal layer 50 having a photonic crystal structure.

A manufacturing method of a photonic crystal layer using a nanoimprintprocess according to a second exemplary embodiment of the presentinvention will be described below with reference to FIGS. 5A to 5C.

Although the manufacturing method of a photonic crystal layer accordingto the second exemplary embodiment uses a nanoimprint process like thefirst exemplary embodiment, the method is slightly different from thatof the first exemplary embodiment. First, a predetermined amount ofpolymer resin in liquid form is coated on one surface of a substrate 10by use of a tool such as a pipette. Then, the polymer resin ispressurized by a mask 100 having an inverted shape of a photonic crystalstructure. In addition, in a state that the polymer resin in liquid formis pressurized by the mask 100, the polymer resin is hardened byirradiating UV rays to the polymer resin or applying heat thereto. Then,the photonic crystal structure of a nanometer size formed on the mask100 can be easily transferred on the polymer resin, thereby forming aphotonic crystal layer 50 having a photonic crystal structure.

FIGS. 6A to 6B are cross sectional views showing the step of forming anintermediate layer on the photonic crystal layer shown in FIG. 4C byusing a sol-gel method.

First, a sol-gel solution 210 is dropped onto a photonic crystal layer50 by using a sol-gel injector 200. Next, the sol-gel solution 210 isspin-coated on the photonic crystal layer 50 by spinning a substrate 10at 1,000-4,000 rpm. Next, an intermediate layer 60 is formed by inducingcrystallization by heating the sol-gel solution 210. By repeating thisprocess, an intermediate layer 60 having a set thickness.

FIGS. 7A to 7C are cross sectional views showing the respective steps offorming an intermediate layer on the photonic crystal layer shown inFIG. 4C and then flattening the surface of the intermediate layer.

As shown in FIG. 7A, an intermediate layer 61 may be formed on thephotonic crystal layer 50 by using methods, such as chemical vapordeposition (CVD), plasma enhanced chemical vapor deposition, evaporatingdeposition, sputtering, as well as the sol-gel method.

By the way, the surface of the intermediate layer 61 formed by thesemethods may not be even in a subtle way due to a recessed and convexphotonic crystal structure formed on the photonic crystal layer 50. Asmentioned above, the conductivity and electrical characteristics of thefirst electrode layer 20 is affected much by its surface shape, andhence it is not preferable to laminate the first electrode layer 20 onthe intermediate layer 61 having an uneven surface.

Accordingly, it is necessary to flatten the surface of the intermediatelayer 61 by using the sol-gel method. That is to say, the surface of theintermediate layer 61 can be flattened by filling a recessed portion 70of the intermediate layer 61 with a sol-gel solution. In other words,the sol-gel solution 210 is dropped onto the surface of the intermediatelayer 61 by using a sol-gel injector 200. Next, the sol-gel solution 210is spin-coated on the intermediate layer 61 by spinning the substrate 10at a high speed of 1,000-4,000 rpm. Next, an intermediate layer 61having an even surface is formed by inducing crystallization by heatingthe sol-gel solution 210. The region filling the recessed portion 70 ofthe intermediate layer 61 is referred to as an even portion 72.

FIGS. 8A to 8C are cross sectional views showing the step of forming anintermediate layer after flattening the surface of the photonic crystallayer shown in FIG. 4C.

As shown in FIG. 8A, though the surface of the photonic crystal layer 50is not even, the surface of the photonic crystal layer 50 can beflattened.

First, as shown in FIG. 8B, an intermediate layer 62 is formed. That isto say, a sol-gel solution 210 is dropped onto the photonic crystallayer 50, then the substrate 10 is spun at 1000-4000 rpm, and when thespaces on the photonic crystal structure are filled with the sol-gelsolution 210, the surface of the photonic crystal layer 50 is flattened.Next, an intermediate layer 62 is additionally formed on the surface ofthe photonic crystal layer 50 according to any one of methods includingchemical vapor deposition (CVD), plasma enhanced chemical vaporDeposition, evaporating deposition, and sputtering.

FIG. 9 and FIG. 10 are graphs comparatively illustrating the lightemission amount of the organic light emitting device having a photoniccrystal structure shown in FIG. 1 and the light emission amount of anorganic light emitting device having no photonic crystal structure inthe prior art, respectively, by simulation.

The graphs shown in FIGS. 9 and 10 are results of a simulation carriedout by using an organic light emitting device whose light sourcewavelength is 511 nm and whose photonic crystal parameters are D=265 nm,A=530 nm and T=120 nm, respectively. Further, the graphs representnumerical values of an electromagnetic field by using an FDTD (FiniteDifference Time Domain) method.

The graph shown in FIG. 9 is a result of a state in which a light sourceis operated by a pulse. The light source is adapted to be turned off ata certain point of time. Further, the light source is modeled as adipole source having a polarization in a certain direction at a certainposition in a similar way to an actual situation, and the polarizationdirection and phase are continuously changed at a certain point of time.

Referring to FIG. 9, the organic light emitting device having a photoniccrystal structure continuously emits light even after the light sourceis turned off. Furthermore, the organic light emitting device having aphotonic crystal structure showed improvement of optical efficiency byabout 200% after two pico-seconds. On the other hand, the organic lightemitting device having no photonic crystal structure has a smaller lightemission amount than the organic light emitting device having a photoniccrystal structure has, and there was not change in light emission amountafter the light source disappears.

FIG. 10 is a result obtained under the same condition as the simulationcondition of FIG. 9 except that the light source is adapted tocontinuously generate light. In this case, the organic light emittingdevice having a photonic crystal structure shows a larger light emissionamount than the organic light emitting device having no photonic crystalstructure does.

FIG. 11 is a graph comparing light emission amounts according towavelength by using the organic light emitting device having a photoniccrystal structure shown in FIG. 1 and the organic light emitting devicehaving no photonic crystal structure.

FIG. 11 is a result of examining a change in light emission amountaccording to wavelength of light by using the parameters of the organiclight emitting device of FIG. 10. The organic light emitting devicehaving a photonic crystal structure has a photonic crystal structureformed by a nanoimprint process, and is provided with an intermediatelayer (made of Si₃N₄) having a thickness of 500 nm by plasma enhancedchemical vapor deposition. As a result, it can be seen that the lightemission amount of the organic light emitting device having a photoniccrystal structure is improved by up to about 50% though the lightemission amount varies with the wavelength of light.

FIGS. 12 and 13 are views showing a character represented by using theorganic light emitting device having a photonic crystal structure shownin FIG. 1.

As shown in FIGS. 12 and 13, the organic light emitting device accordingto the exemplary embodiments of the present invention makes light to bescattered and diffracted by having a photonic crystal structure.Accordingly, a character or picture is made noticeable by using theorganic light emitting device according to the exemplary embodiments ofthe present invention, thereby improving visibility and representing acharacter or picture that emits a unique light. Subsequently, theorganic light emitting device according to the exemplary embodiments ofthe present invention can be applied in a variety of display fields,such as advertising lighting requiring high visibility, as well asgeneral lighting.

For instance, as shown in FIG. 12, when the parameters of the photoniccrystal structure are set differently at a region where characters“KIMM” are positioned, the characters “KIMM” can be further noticeable.

In addition, as shown in FIG. 13, when the photonic crystal structure ata specific region is removed by etching or mechanical etching ormechanical removal, the specific region having no photonic crystalstructure can be seen as a character “K”.

In this manner, the organic light emitting device according to theexemplary embodiments of the present invention can be widely used aslighting which makes it easier to visually identify and produces aunique light.

Although the exemplary embodiments of the present invention have beendescribed, the present invention is not limited thereto, and a varietyof modifications can be made within the scope of the claims, thedetailed description of the invention, and the attached drawings, whichare also included in the present invention.

1. An organic light emitting device, comprising: a substrate throughwhich light passes; a photonic crystal layer formed on the substrate andhaving a photonic crystal structure without voids therein; anintermediate layer formed on the photonic crystal layer and having arefractive index that is greater than a refractive index of the photoniccrystal layer; a first electrode layer formed on the intermediate layer;a light emitting layer formed on the first electrode layer and emittinglight according to current flow; and a second electrode layer formed onthe light emitting layer, wherein the photonic crystal layer is made ofan ultraviolet (UV)-cured polymer resin and the substrate is a glass orsapphire substrate, wherein the entire surface of the intermediate layeron which the first electrode layer is stacked is even.
 2. The organiclight emitting device of claim 1, wherein the refractive index of thephotonic crystal layer is less than or equal to a refractive index ofthe substrate.
 3. The organic light emitting device of claim 1, whereinthe refractive index of the intermediate layer is greater than or equalto a refractive index of the first electrode.
 4. The organic lightemitting device of claim 3, wherein the intermediate layer is made ofone material selected from the group consisting of oxides and nitrides.5. The organic light emitting device of claim 3, wherein theintermediate layer is made of one or more materials selected from thegroup consisting of SiNx, Si₃N₄, TiO₂, MgO, ZnO, Al₂O₃, SnO₂ and In₂O₃.6. The organic light emitting device of claim 1, wherein a sol-gelsolution is coated on the intermediate layer.
 7. The organic lightemitting device of claim 1, wherein the photonic crystal structure formsa lattice structure by having a plurality of photonic crystal unitsregularly arranged thereon.
 8. The organic light emitting device ofclaim 7, wherein the photonic crystal structure forms a square latticestructure by having a plurality of photonic crystal units regularlyarranged thereon.
 9. The organic light emitting device of claim 7,wherein the photonic crystal structure forms a triangular latticestructure by having a plurality of photonic crystal units regularlyarranged thereon.
 10. The organic light emitting device of claim 7,wherein a shape of the photonic crystal units is one of a cylinder, atrigonal pyramid, or a square pyramid.
 11. The organic light emittingdevice of claim 1, wherein the first electrode layer is made of atransparent conducting oxide (TCO) material.
 12. The organic lightemitting device of claim 1, wherein the polymer resin, which is in aliquid form, is coated on one surface of the substrate to be cured bythe UV.